Safety apparatus for hydraulic elevator jacks

ABSTRACT

The soil-embedded, subterranean portion of a hydraulic elevator jack or cylinder is sealingly encased in a fiber glass reinforced plastic housing to protect the jack from electrolysis and corrosion. A pressure responsive safety circuit communicates with the interior of the plastic housing and is operable to detect a leak in the jack and automatically interrupt the conventional controls for the elevator and cause a gradual, safe descent of the elevator to ground level.

United States Patent [191 Moseley et a].

[ SAFETY APPARATUS FOR HYDRAULIC ELEVATOR JACKS lnventors: Wallace Frederick Moseley; Robert F. Schnetzer, both of Columbus, Ohio Plunger Lift Elevator, Inc., Columbus, Ohio Filed: Mar. 30, 1971 Appl. No.: 129,450

[73] Assignee:

US. Cl 91/451, 91/459, 92/77, 92/86 Int. C1.F0lb 29/00, F15b 13/042, Fl5b 13/044 Field of Search 92/77, 86; 91/451, 91/459; 60/52 HD [56] References Cited UNITED STATES PATENTS 1,686,825 10/1928 Lisle et al. 92/77 June 26, 1973 2,891,635 6/1959 Joseph ..92/77 3,065,738 11/1962 Loughridge ..92/77 Primary Examiner-Paul E. Maslousky Attorney-William S. Rambo [57} ABSTRACT The soil-embedded, subterranean portion of a hydraulic elevator jack or cylinder is sealingly encased in a fiber glass reinforced plastic housing to protect the jack from electrolysis and corrosion. A pressure responsive safety circuit communicates with the interior of the plastic housing and is operable to detect a leak in the jack and automatically interrupt the conventional controls for the elevator and cause a gradual, safe descent of the elevator to ground level.

3 Claims, 3 Drawing Figures AQ Q T SAFETY APPARATUS FOR HYDRAULIC ELEVATOR JACKS BACKGROUND OF THE INVENTION In most hydraulic elevator installations, at least a part of the hydraulic jack or ram extends below the ground level and is embedded in the soil. In such an installation, the metal hydraulic cylinder is directly exposed to the surround soil orearth and is thus subjected to rather rapid corrosion, pitting and deterioration due to both chemical and electrolytic action. When sufficient deterioration occurs, the cylinder will rupture and allow loss of hydraulic fluid and fluid pressure and consequent dangerous uncontrolled descent of the elevator. If the rupture is sudden and substantial, the elevator may drop causing possible serious injury and damage.

In an effort toalleviate this problem, it has been proposed to encase the subterranean portion of the hydraulic elevator cylinder within a protective housing or false cylinder to isolate and protect the hydraulic elevator cylinder against electrolytic and/or chemical attack. Such a proposal is shown and described in prior U.S. Pat. to Loughridge No. 3,065,738 issued Nov. 27, 1962. It isinteresting to note, however, that in these prior art constructions, the outer protective casing or. false cylinder was also formed from a metal or metal alloy which-was subject to' electrolytic corrosionand deterioration at substantially the same rate as was the unprotected 'typeof hydraulic cylinder. 'Also, in the case of the apparatusproposed in the aforesaid Loughridge patent, the outer protective casing or cylinder was placed in fluid communication with the pressure chamber of the main hydraulic jack, so that if and when a leak occurred in the outer protective housing, a leak, albeit small and restricted, also occurred in the hydraulic jack.

There is therefore a need for a safety apparatus which will not only protect the subterranean portion .of the hydraulic elevator jack from electrolytic deterioration, but which will additionally detect a leak which might occur in the subterranean portion of the jack and function automatically to cause a safe descent of the elevator to ground level and a temporary disabling of the normal elevator controls until the leak is repaired.

' SUMMARY AND OBJECTS OF THE INVENTION The present invention provides improved protective apparatus for a hydraulic elevator jack in which a corrosion resistant outer housing, sealingly encases the subterranean portion of the elevator jack to shield it from contact with moisture and the surrounding soil. This outer housing is spaced from the hydraulic cylinder of the jack to define an intermediate fluid chamber.

An electrical safety circuit is associated with the inter-- mediate fluid chamber and is operable in response'to an increase in fluid pressure in the intermediate chamber, such as would be occasioned by a rupture or leak in the main pressure cylinder of the elevator jack, to cause a gradual, safe descent of the elevator to ground level and to interrupt the normal, manual control system for the elevator.

The primary object of the invention is to provide safety apparatus for a hydraulic jack-type elevator which protects the hydraulic jack against undesired electrolytic deterioration and which protects the elevator and its occupants against damage and injury in the event of a leak or rupture of the soil embedded portion of the hydraulic jack.

Further objects and advantages of the invention will be more readily apparent from the following description when considered in connection with the accompanying drawings which illustrate a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in vertical section showing a hydraulic jack-type elevator equipped with safety apparatus according to this invention;

FIG. 2 is anenlarged vertical sectional view taken through the hydraulic elevator jack and the outer protective casing; 1

FIG. 3 is a schematic diagram of the electrical safety circuit which forms a part of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION While specific terminology is used to describe the preferred embodiment of the invention,as illustrated in the accompanying drawings, it should be understood that such terminology is intended to include allstruc- .tural equivalents which operate in a similar'manner to accomplish a similar result.

Theelevator system illustrated in FIG; 1 includes the usual vertically extending elevator shaft 10 which terminates at its lower end in a pit floor l2, and which contains a vertically reciprocatable elevator platform or car 14. The elevator platform 14 is'lifted by a hydraulic elevator jack assembly, indicated generally at 16, and which is mounted on the floor 12 of the elevator pit and extends vertically beneath the pit floor 12 into the earth or soil l8. r

The hydraulic elevator jack assembly 16 isillustrated in greater detail in FIG. 2 and comprises a hydraulic pressure cylinder 20 and a relatively telescoping, axially extensible and retractable ram or plunger 22. The cylinder housing 20 is preferably fabricated from a seamless steel tube which is closed by a plug 24 welded in its lower end. An annular mounting flange 26 is welded to the upperend of the cylinder 20. The plunger 22 extends outwardly' from the upper end of the cylinder and is secured to the elevator platform 14 by means of a bolted flange fitting 28. The plunger 22 the adjustable packing gland 44 serves as a guide bearing for the plunger 22. An annular oil collector ring 46 is welded in surrounding relation to the mounting flange 26 so as to collect any hydraulic oil or fluid which may leak past the packing 42 and direct such fluid through an overflow tube 48 into a suitable receptacle or drain in the elevator pit.

An inlet-outlet conduit or pipe 50 is connected with the upper end of the cylinder 20 to conduct pressure fluid to and from the pressure chamber in the cylinder. The pipe 50 is connected in the usual manner with a conventional valve-controlled hydraulic pump and reservoir system, not shown, by means of which fluid under pressure may be alternately supplied through the conduit 50 to the cylinder 20 to extend the plunger 22, or' exhausted from the cylinder 20 by way of the conduit 50 to cause retraction of the plunger by gravity.

As will be understood, normal operating movement of the elevator to and from different levels is controlled by a system of manually operated switches which are connected in a conventional solenoid-operated hydraulic valve and pump circuit so that hydraulic fluid under pressure is either supplied to or exhausted from the hydraulic cylinder 20 to selectively raise or lower the elevator l4.

In accordance with the present invention, the subterranean portion of the hydraulic jack cylinder 20 is encased within an outer, corrosion resistant cylinder or casing 52. The outer cylinder 52 is spaced from the hydraulic pressure cylinder 20 to provide an intermediate chamber 54 which is preferably filled with hydraulic fluid under-atmospheric pressure. The protective outer casing 52 is preferably fabricated from a fiberglass reinforced synthetic resin which is resistant to attack both by hydraulic oil or fluid and by the surrounding soil. A circular plastic closure plug 56 is bonded and sealed in the lower end of the outer casing 54 and is provided with a central, recessed seat or counterbore 58 to receive and center the lower end of the hydraulic cylinder 20. The upper end of the outer casing 52 is closed by an annular sealing ring 60 bonded to the interior of the outer casing 52 and to the exterior of the cylinder 20. A port 62 extends through the sealing'ring 60 and provides communication with the chamber 54.

A relatively small conduit or pipe 64 extends from the port 62 to a remotely located diaphragm or bellows-type pressure responsive switch 66 shown diagrammatically in FIG. 3. The pressure responsive electrical switch 66 is normally open, but is arranged to be closed in response to a predetermined positive fluid pressure within the intermediate chamber 54, such as might be occasioned by a leak or rupture within the wall of the hydraulic cylinder 20. The terminals 67 and 68 of the pressure responsive switch 66 are connected in series between the power lines L1 and L2 with the coil 72 of a multiple pole relay 70. Closure of the contacts of the pressure responsive switch 66, in response to a pressure increase in the chamber 54, energizes the coil of the relay. The relay includes a normally open set of contacts 74 and 76 which are electrically connected in a hold-in circuit for the coil of the relay. This relay hold-in circuit also includes a normally closed reset switch 78. The hold-in circuit is thus operable to maintain the relay coil 72 in an energized condition once the pressure responsive switch 66 has been actuated and until the reset switch 78 is opened. The relay 70 also includes a second set of normally open contacts 80 and 82 which are connected in series circuit with the solenoid 84 of a bleed-off valve V. The bleed-off valve V is connected with the inlet-outlet conduit 50 of the pressure cylinder 20 and is normally closed. However, upon energization of the solenoid 84, the valve V is opened to permit hydraulic fluid to be exhausted from the cylinder 20 at a relatively slow and controlled rate, thus effecting a gradual descent of the elevator platform 14 to its lowermost ground floor position.

The relay 70 includes a third set of normally closed contacts 86 and 88 which are connected in the conventional manually operated elevator control switch circuit, shown in block diagram in FIG. 3, so as to disable .ate a bottom landing call upon energization of the relay switch 70.

OPERATION In operation, the pressure-responsive switch 66 remains open so long as the fluid pressure within the chamber 54 is below a predetermined positive pressure. This permits normal operation of the elevator 14 by means of its conventional, manually operated control system. However, if and when a break or leak should develop in the encased portion of the hydraulic jack cylinder 20, the pressure'within the cylinder 20' will be applied to the fluid within the surrounding chamber 54 and to the pressure-responsive switch 66 by way of the pilot conduit 64. This increase of pressure within the chamber 54 and conduit 64 will result in closure of the contacts 67 and 68 and energization of the coil 72 of the relay switch 70. Energization of relay switch 70 results in closure of the hold-in contacts 74 and 76 and the bleed-off valve controlling contacts 80 and 82. Closure of contacts 80 and 82 causes energization of solenoid 84 and the opening of the bleed-off valve V. This, in turn, causes the elevator platform 14 to descend slowly by gravity to its lowermost level. Simultaneously, the third set of contacts 86 and 88 are opened to interrupt or disable the manually operated control circuit of the elevator, and prevent further operation of the elevator until the safety circuit is restored or reset.

In view of the foregoing, it will be seen that this invention provides a mechanically simple, yet efficient and effective safety system for protecting the soilembedded portion of a hydraulic elevator cylinder or jack against electrolytic and/or chemical corrosion and, at the same time, provides means to insure a safe descent and an interruption of the normal operation of the elevator in the event of a rupture, break or leak in the embedded portion of the hydraulic cylinder.

While a preferred embodiment of the invention has been illustrated and described in detail it will be understood that various modifications as to details of construction and design are possible without departing from the spirit of the invention or the scope of the following claims.

We claim:

1. In combination with an elevator having a hydraulically actuated jack with a cylinder including a subterranean portion and a manually operated electrohydraulic control circuit operable normally to control the up and down movement of said elevator:

a. an outer housing of corrosion-resistant composition sealingly encasing the subterranean portion of said hydraulic cylinder and defining therewith a normally non-communicating, generally closed fluid chamber; and

b. switch means connected with the electrical control circuit of said elevator and operable in response to a given increase of pressure in said fluid chamber to disable the electrical control circuit of said elevator against manual operation and to cause said elevator to descend at a controlled rate to its lowermost level.

2. The combination according to claim 1, wherein said elevator. 

1. In combination with an elevator having a hydraulically actuated jack with a cylinder including a subterranean portion and a manually operated electro-hydraulic control circuit operable normally to control the up and down movement of said elevator: a. an outer housing of corrosion-resistant composition sealingly encasing the subterranean portion of said hydraulic cylinder and defining therewith a normally non-communicating, generally closed fluid chamber; and b. switch means connected with the electrical control circuit of said elevator and operable in response to a given increase of pressure in said fluid chamber to disable the electrical control circuit of said elevator against manual operation and to cause said elevator to descend at a controlled rate to its lowermost level.
 2. The combination according to claim 1, wherein said outer housing is composed of a glass fiber reinforced synthetic resin.
 3. The combination according to claim 1, wherein said switch means cOmprises a normally open pressure-responsive switch in fluid communication with said fluid chamber, and a relay switch energizable upon closure of said pressure-responsive switch and having contacts electrically connected with the control circuit of said elevator. 